tritle



J. F. TRITLE.

SYSTEM OF MOTOR CONTROL. APPLICATION FILED JUNE 20, I916.

Patented July s, 1919.

2 SHEETSSHEET l.

Inventor". ohn F rtle, 5

His Attorneg J. F. TRITLE.

SYSTEM OF MOTOR CONTROL.

. APPLICATION FILED JUNE 20,- 1916.

Patented July 15; 1919.

2 SHEETSSHEET 2.

Inventor John Fjmtle, bg a His fitter-neg.

In! IIIIIIIIII'IIIIIJ'IIIIIII 0 SPATENT. OFFICE.

UNITED sirAT JOHNI, TRI'ILE, or scnnnncrenr, NEW YORK, assumes. noonnnmnnmcrmo I COMPANY, A CORPORATION or NEW YORK.

SYSTEM or Moron CONTROL} nsfobao.

Specification of Letters Patent.

\ l Application filedl'une 20, 1916. Serial No. 104,721.-

To all whom it may concern: 7

Beit known that I, JQI-IN'F. Turns, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Systems of MotorControl, of which the following is a specificatio This invention relatesto the control of electric motors and has for its object the provisionof improved means whereb electric motors are started, stopped angerierally controlled in asimple, reliable and efficient manner. Y

lVhile my invention is capable" of general applic'atjpn in the motorcontrol field, it is otpgrtrhlar importance in the control of electric-railway n1otors.' y

In an application of Frank E. Case, Se-

rial No. 33,496, filed June 11', l915,'patented .April 3, 1917, No,1,221,676, an improved system of motor control is disclosed in which ithe switches for making the various changes in-the motor circuit areforced to operate in a predetermined order by mechanical means, thusproviding a control which has advantages because of its lightweight, andwhich obviates the complications which are inherent in a systememploying electromagnetic switches or contactors having interlocks forbringing about the required order of progression of the contactors. Inthe said application of Frank E. base, which shows and describes myinvention, but makes no claim thereto, a control system for electricmotors 18 provided, in which a plurality of unit switches make thevarious motor conmotions; in ascriesmrallel control system, and theseunit snatches are forced to close against a spring tension by means ofcams which in'tnrn are opc'rated by a main con troller which is underthe control of a. master controller. The motor for adyancing the maincontroller in a step by step manner to make the various changes int-hemotor cirtroller, and prevents this contro'llr":"from being moved fromone circuit-closing posh tion to the next in succession until the motorcurrent at each position has dropped to a predetermined value.

One of the objects 'of my invention 1's to provide a system in which thecontroller which makes the changes in the motor circuits will take acomplete step from one circuit-closing )osition to the next insuccession, althoug it is under the control of the current-limit deviceat the beginning of movement.

Without such an arrangement as I procrate after the main controller hadbegun its movement from one of the operative positions to the next insuccession, or in case. the operator moved the master controller onestep forward'and then before the main controller had completed itsmovement, he moved the master controller backward one step, the maincontroller would be left in a mid position between the proper operativebe caused at the'main controller contacts, but the operation of the maincontroller would not be sufficient to complete a proper operatingcircuit for themotors. I provide a current-limit means whereby the maincontroller, which may be advanced step by step by any suitable means.cannot be moved from one operative position to the next in successionuntil the motor current has dropped to a predetermined value, thearrangement being such that after the motor current has dropped to thepredetermined value, and the operator has moved the master controllerforward one notch. the main one operative position to the next eventhough the motor current should rise above the predetermined value orthe operator should move the master controller backward one step whilethe main controller is taking the step. More specifically, my inventionprovides a main motor operated controller, the step by ste advance ofwhich is under the control o a current-limit relay and ,which hascontacts thereon for short-circuitto render the current-limit relayineffective ment from'oneoperative position to the next 'infsucce'sslionin: response to the movement "of the master controller; The movement ofthe main controller, which makes the changes Patented July 15, 1919.

ing the current-limit relay contacts so as t stop the motion of the mainmotor operated controller afterfit has begun its move vide, if thecurrent-limit device should op- I positions and thus destructive arcingwould controller will be positively moved from the lit , stationarycontact.

.in the motor circuit, is thus independent of the current-limit-relayafter having. started to move from one position to the next, and

the movement must be completed evening'the unit switches, and Fig. 3 isa simpli- 'fied diagram showing only the motor circuits. I

I shall first describe a system. of control embodying my improven'ientsas a whole, and= .-shall then point out more in detail the specificfeatures of my invention.

Looking first at Fig. 1, ,it will be noted that I'have shown aseries-parallel system of motor control in which two motors areemployed. It will be understood, however, that my invention is in nosense limited to the particular system employed or to the number ofmotors controlled. The illlllilr tures of the two motors are designatedA and 'A while the fields which are subdivided as hereinafter describedare designated 'F and F. RS designates the reversing switch as a whole,MC indicates the master controller, and LB and LB represent the two linebreakers. B represents a potential relay which is deenergized so as toreturn the controller to the off position upon the failure of power. ()Rrepresents an overload relay, d) represents a current-limit relay orthrottle, for causing the advance of the main controller to be under thecontrol of the motor current and E represents a battery for energizin.the control circuits.

The main controller, which I have designated M, as shown in Fig. 1,consists of a number of cams arranged upon a shaft so as to close thecontactors in a predetermined order Forming a part of the controller androtated with the cam shaft. are two sets of contacts G and H, thepurpose of. which will be hereinafter described.

The'main controller comprises a number of unit switches, one of whichisshown at K (Fi 2), which switches are operated electro-pneumatically.Each switch con- SlStSfj'Qf an insulating base upon which is 'mounted astationary contact 11, having a magnetic blowout 12, adjacent thereto,and

a contact arm 13 pivoted at 14 and having contact 15 at its end,cooperating with the I The contact arm 13 is normally held in open.position by spring IGQas-"ShQWn,in the drawing and is closed'by with arollen1 8 0n the arm. As before stated, the cams, one of which is shownat 17, are arranged around a shaft 19 and longitudinally thereof, asshown in Fig. 1. The cam surfaces have the proper lengths, as indicatedin Fig. 1, to maintain the switches closed for a proper interval. The-cam shaft 19 is rotated through the pinion 20 by a pneumatic motorcomprising a rack 2.1 having a piston at each end. These pistops 22 and23 operate in cylinders 24 and 25 respectively, to which compressed airis admitted through the ports. 26 and 27 respectively. The port 26 isnormally closed to reservoir and open to atmosphereby theelcctromagnetically-operated valve 28 and is opened by the energizationof the magnetiv ing winding of the valve, while the port 27 iscontrolled by the normally open electromagnetically-operated valve 29.This latter valve isclosed when the magnetizing winding is energized.The valve 28, which as above stated is normally closed, connects thecylinder to atmosphere when the winding is decnergized, but, when thewinding is energized, connects the port 26 with the air reservoir so asto admit con'ipressed airto the cylinder 24- so as to move the piston 22to the left; The valve 29 which is nor mally open controls the passagefrom the reservoir to thecylinder so that in the normal position of thevalve, with the mag I netizing winding deenergized, there will be fullreservoir pressure in the cylinder 25. \Vhen, therefore, the magnetizingwinding of the valve 28 is energized, compressed air will 'be admittedto cylinder 24. for moving piston 22 to the left, this being themovement which turns the cam shaft in the on direction, that is, tooperatethe proper switches to bring the motors up to speed. Thismovement will not take place,however, (except as to the first step ashereinafter described) unless the pressure is exhausted from thecylinder .25 by the operation of the valve-29 which closes theconnection between the cylinder and the reservoir, and opens theconnection between the cylinder and atmosphere. When, however, the valve29 is opened by the deenergization of its winding, fullreservoirpressure is admitted to the cylinder 25 so that the pressure onthe two pistons 22 and 23 will be balanced. There-' fore when themagnetizing winding of the valve 28 is energized, and the magnetizingfixedly connected to the rack 21, the piston f2 not soconnected with therack but forward until the spring 31 is. fully-cone press'etL- Thismovement causes the cam shaft .to move one step to close the motorcircuit as will hereinafter appear.

()n" the top of the cylinder casing is the reverse switch RS comprisinga drum A and means for operating the same. The drum is operatedpneumatically bymeans of a doubleacting piston 32 connected with the"breaker is provided with twointerlocking contacts 42 and 43. Theclosing of the con: tact i2 by tlie closing of the line breakerenergizes :the magnetizing winding of electromagnetic valve 28, which Ishall call the on" magnet, the circuit being from the cylinder by arm 3The movement tollljlkt, the forward connections for the motors iscontrolled by electromagnetic valve 7. while the movement in thedirection to connect the motors for reverse operation-is are firstclosed, switch 31 being closed on 'its left-hand contact.

switch 35 energizes the potential relay .13 having contacts 37 and 38from the trolley T to the winding of the relay, through resistance 1" tobridging contact 36 on the main controller, and thence toground. If,now, the mastercontroller MC is moved to the first position. a, thereversing switch will be operated by the energization of thoelectromagnetic valvef in 'case the reverser should be in the wrongposition." As shown, however, the reverser has been left in the forwardposition so that there is no change with reference to this switch. Theline breaker LB now closes, being energized from the battery, throughthe conductor 39,

the contact 40 on the main controller, conductor 41, contact. 37 on thepotential'relay The closure of the batter v'=thro ugh the interlockingcontact 40 through ,interlocking contact 42, thence through interlockingcontacts 38 and 4-1:, back to the battery through the master controller.The energization of the on magnet while the off magnet valve 2 isdeenergized, car'ses the cam shaft to move one step by compressing thespring 31 while the piston 21 is held stationary by the pressure agalnstit in a manner previously described. This has the"etl'ectof closingthecontacts 11 and lothrougirthe agency of-the am 17. The motor circuitwillnow be closed from the trolley T through the switch 35 and thewinding of overload relay OR, the contacts of line breaker-LB, throughresistance B, through the contacts on the reversing switch "RS, a'matureA, two sections of field winding F, through the re sistance-R'.R"contacts 11 and 15, resistances R and K, through the two sections offield winding F and thecontacts on the reversing switch, armature A,thence to the throttle or relay D and to ground. The closing ofthe motorcircuit therefore is effected at thecontacts 11 and 15 of one of theunit switches. The'motors will now run in series with all the resistancein circuit.

\Vhen the master controller is moved to position r),'the line breaker LBwill be closed; the circuit being from the batter), through wire 47,interlocking contact *8, interlocking contact 43 on line breaker LB,through the contacts controlled by the throt tle magnet D and throughone of the 'con- -tacts G on the main cont-roller, thence to the -mastercontroller and back to the battery.

Line breaker LB'- will therefore close and shortcircuit.tlre resistanceR and in closing energize the off magnet of the electromagnetic valve29, through the contacts 4!).

- The energization of the off magnet causes the cylinder25 to beexhausted to atmosphere so that the two pistons 23 and 22 .move forwardcausing'the cam shaft to and contact 37 on the overload rela v,-

throughcontacts on the reversing switch and the-master controller backto the bat- The line move a second step and the cam 50 to close thecontacts 51, and short-circuit the two sections of resistance R and RThe invention thus far described forms no part of my invention but isthe invention of Frank E. Uaseand forms part of his application abovereferred to. v

I shall 'nbwdescribe my invention in detaiL. Itis'to be here noted thatthe pneumatic operating means of the Frank E. Case application abovereferred to has been chosen -for the purposes of illustration and is mypreferred form of .m'otor,.b'nt any suitable means may be used foradvancing the main controller-step by step to make the various changesin the motor circuits.

Upon the cutting out of each of the resistance sections it, It and R themotor current rises sothat the throttle D will open its contacts toprevert the controller being moved another step until the current dropsone of the contacts 1-1. This makes a cireuit in parallel with thecircuit through the throttle contacts, this parallel circuit beingthrough contacts 38 and 44 on the potential relay B and overload relayOR respectively. The coil 56 is included in this circuit to assist theseries coil and makethe throttle more sensitive to changes of current.It is advisable that the advance of the controller be momentarilyretarded at each operative position so as to prevent too rapidacceleration and prevent the controller moving through an operativeposition and causing a heavy rush of current at the next operativeposition. that the current limit throttle will open its contacts whilethe controller is moving from one step to another during acceleration.The shunt coil 56 willpositively pick up the throttle D during thetransition from one step to another, and then the throttle -will closeafter the step is completed, re-

sponsively to the motor current. .Furthermore, by means of this coil 56the throttle I) need only be calibrated for'its drop out value, since itis positively picked up during the transition from one step to theother. The throttle may therefore open, but the movement of the camshaft willhot be interrupted until the circuit is interrupted at contactH and established on the second contact (i, which, it will be observed,will be when the controller has completed a step to position b. If,therefore, the currenthas not dropped to the proper alue when the camshaft has completed its step. it cannot take another step until thecurrent does drop so as to energize the off magnet through the throttlecontacts. When the current does drop to a proper value, the off magnetwill again be energized to cause the am shaft to take another step whichshort-circuits the res ista1-u:e K through ,ram 50.-

Again the throttle will preventfurther To take care of this I insurewillshort-circuit the resistance R. When the cam shaft moves to the nextstep (0' on the main controller) in which the fields of the motors aretapped to give increased speed, the progression will stop, by reason ofthe fact that one of the contacts G, marked 52, is oifset from theothers so as'to interrupt the circuit of the off magnet through bothsets of contactsG and H. In order to progress further, it is necessaryfor the master controller to be moved to position 0 in which the offmagnet is energized through the contacts 53, on the master controller,and the contact 52 which engages with contact finger 54;. The movementof the master controller to the position 0, therefore, causes the camshaft to take one step (to position 0) which changes the motorconnections from full series with tapped or weakened field, which is thehighest speed positionin series, to the parallel position. When thisposition is reached, the progression is stopped by reason of the factthat I the contact 54 passes over the contact 52:

In order to progress further, it is necessary the electromagnetic valve28. This will exhaust the cylinder 24; to atmosphere so that thepressure in cylinder 25 will move the rack 21 to the right and henceturn the controller back to oif position. This dot ncrgization of theon-- magnet to turn the controller will be accomplished by thedeenergization of the potential relay B. Iffor instance, the powershould fall, even foran instant, 'the potential relay will drop therebydeenergizing the on magnet at the contact 38 of the relay. It will benoted that this potential relay is energized through the contact 36 inthe olf position of the main controller, but that as soonas thecontroller moves from off position a holding circuit is made through aresistance r. If,

therefore, the potential relay should open,.

it (fan only be closed if the niain controller is in the off position.The rc=erser IRS is also interloclu-d with the main controller atcontact 40 so that the valve magnetsf and r can only be energized in theoff position of the controller. The opening of .the potential relaycauses the opening of the line breaker LB which in turn causes theopening of the line breaker LB and causes 1 another break 'inthejcircuit of the on magnetso that the controller wi1l be returned tooffposition. It will be under stood of course, that at any time when thebetween positions by moving'back one step on the master controller,which will deemergize the oil magnehand balance the pressure in the twocylinders. For 1nstance, if the master controller is in position I b andthe main controller is advancing to make the various connections inseries, pro gression may be stopped by bringing the master controllerback to' the position a. Likewiseif the master controller is in positionat the automatic progression may be stopped by moving the mastercontroller back to the position 0. hen the master controller is moved tothe off position, the

magnet will be deenerglzed and the f main controller returned to offposition.

Upon the occurrence of an overload, the overload relay OR will cause themotor circuit to be opened at the line breakers and stop the motors.This overload relay is of the reset type, that is, when it opens it islatched open. The line breakers cannot be closed until the overloadrelay is reset and then can. only be closed by moving the switch 34 onto its right-hand contact which will energize the magnet 55 to releasethe latch and allow the relay to close theopcrating circuits of the linebreakers.

While I have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of thepatent statutes, it should be understood that Ido not limit my inventionthereto, since various modifications thereof will suggest themselves tothose skilled in the art without departing from the "nirit of myinvention, the scope of which is forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

The combination with a controller for starting electric motorsfof meansfor causing the controller to advance step by, step under the control ofthe motor current, and means whereby the current control is renderedmore sensitive only when the controllcr is being advanced from one stepto the next and after a step is begun the advance of the controller isrendered independent of the motor current until the step is completed.

2. The combination with a controller for starting electric meters, of acurrent-limit device for causing a step by step advance of thecontroller under the control of the motor current, and means whereby thecurrent limit device is rendered more sensitive. only when thecontroller is being advanced from ionei step to the next and after astep7 begun the advanceof the controller 15 rendered independent of thecurrent-limit device.

3. The combination with an electric motor and a controller therefor, ofa'current limit device for causing the controller to advance step bystep under the control of the motor current, means for insuring theoperation of --the current limit device while thecontroller is movingfromone operative position to .the next, and meanswhereby after a stepisbe- I gun the advance of the controller is rendered independent of thecurrent limit device until the step is completed. v

4. The combination with an electric motor and a controller therefor, ofa current-limit device for causing the controller to advance step bystep under the control of the'mot'or current, a shunt coil for thecurrent limit device, and means whereby the shunt jc'oil is energizedonly during the transition from one-step to the next and after a: stepis begun the advance of the controller is rendered independentof themotor current until'the step is completed. v f

5. The combination with an electric'motor and a controller therefor, ofa currentlimit relay for causing a step by step advance of thecontroller under thecontrol of the motor current, a shunt coil for thecurrent limit device and means including short-circuit around thecurrent-limit relay contacts and through the shunt coil whereby afterthe movement of the controller from one operative position to the nexthas begun the controller will take a complete step independently of thecurrent-limit relay and the current limit relay rendered more sensitiveduring the transition from one step to another.

6. The combination with an electric motor and a controller therefor, ofa current limit relay for causing a step by step advance of thecontroller under the control of the motor current, contacts on; thecontroller for interrupting the circuit through the contacts on thecurrent limit device at each step and additional contacts on thecontroller for short circuiting the contacts of the current limit deviceafter a step has begun, so that the controller will take a complete stepindependently of the current limit relay.

7. The combination with a plurality of electric motors and a seriesparallel control- 1 ler therefor, of a current limit relay for causing astep by step advance of the controller under the control of the motorcurrent, contacts on the controller for interrupting the circuit throughthe contacts on the current limit relay at each step, addi- 'tionalcontacts on the controller for short pendently of the current limitrelay, and

means comprising a contact on the controller for interrupting thecircuit through the contacts on the current limlt device so that theadvance of the controller is interrupted "at the full series position.

8. Means for controlling electric motors comprising a main controllerforthe motor circuit, pneumatic operating means for advancing the maincontroller step by step, a master controller for controlling thepneumatic operating means, a current-limit device governing theoperation of the pneumatic operating means for causing the advance ofthe main controller to be under the control of the motor current, andmeans whereby after the mastercontroller has been moved a step forwardand the pneu' lnatic operating means has begun the move ment of the mamcontroller from one operative position to the next, the pneumaticcircuit, pneumatic operating means there for,electroma-gnetically-actuated valves for controlling the main controllerto cause it to advance step by step, a, master controller forcontrolling the electromagnetically-operated valves, acm'rent-limit'relay for causing the advance of the main controller to beunder the control of the motor current, an operating circuit for oneofthe electromagnets through a contact on the main controller and thecontacts of the current-limit relay at each operative position of themain controller, and means comprising a contact on the main controllerfor shoit-circuiting the contacts of the current-limit relay ,after themaster controller has been moveda step forward and the movement of themain controller from one operative position to the .next has begun,whereby the electromagnetically-operated valves are independent of the'current-limit relay until the main controller has taken a complete step.

In witness whereof, I have hereunto Set my hand this 15th day of June,1916.

JoHN r. TRITLE.

